The present invention relates to a method of preparing an organic-inorganic polymeric water-retaining fertilizer. Through a reaction in which a macromolecular water-absorbing resin and an inorganic nutrient factor are fused and co-polymerized, a novel water-fertilizer-retaining material is made, well, this material has functions of integrating of water and fertilizer as well as retaining of both water and fertilizer, functions of sustained releasing synchronously as well as double controlled releasing of both water and fertilizer, a function of resisting to pests and diseases, a function of regulating of soil, etc.
Related technical indexes: content of organic matter is ≥20%; water absorbency is of 10 g/g-20 g/g; the total content of nutrients of nitrogen, phosphorus and potassium is 35%-40%; the total content of nutrients of secondary elements of calcium, magnesium, silicon and sulfur are ≥5%; the release rate of nutrients at the initial stage is ≤15%. (Executive Standard of “Organic-inorganic Polymeric Water-retaining Fertilizer” of the present enterprise: Q/370203XYD 001-2016).
Chemical fertilizers are the largest material investment in agricultural production globally. According to the statistical information from Food and Agriculture Organization of the United Nations, in terms of improving the unit yield, the effect of chemical fertilizers on yield increase accounts for 40%-60%. The production practice shows, however, that the utilization rate of chemical fertilizers is quite low due to the combined influences of the properties of the chemical fertilizer itself, environmental conditions of soils and agricultural practice. The waste of nutrient resources in China is quite astonishing as a result of the low utilization rate of the nutrients of the fertilizers. The newest data from authorities reveals that, due to the blind and excessive fertilization by peasants in China, the direct economic loss reaches 650 CNY per hectare, with an environmental cost being approximately 73 billion CNY and annual flow-away of fertilizers being more than 110 billion CNY. It has been a commonly concerned problem among countries worldwide regarding how to improve the utilization rate of chemical fertilizers, to reduce the problem of environmental pollution caused by inadequate fertilization, and to develop high-efficiency agriculture in a sustainable manner.
Since the beginning of the 21st century, the development, preparation and application of water-retaining fertilizers have offered a new idea for solving this problem. The development and preparation of an integration of a water-retaining agent and a fertilizer have become a cutting-edge technological hotspot for researches on fertilizer worldwide, and the technologies of organic-inorganic combining and coating have been developed. Ever since the development and preparation of the water-retaining sustained- and controlled-release fertilizer, the technology of sustained release by compounding water-retaining agents and inorganic nutrients as well as the technology of sustained release by coating with water-retaining agents have undergone applications and development. Based on the development progress, there are representative categories for modern technologies of resin coating as follows. One of the representative categories is the technology of sustained release by compounding water-retaining agents and inorganic nutrients. The key technology thereof is the ratio for preparing and compounding the water-retaining agents and the inorganic nutrients. Since the technology employs a physical blending of the water-retaining factor and the inorganic nutrient factor, the property of sustained release for nutrient thereof is restrained; and due to the high cost of the water retaining agent, it fails to be applied to the actual production in large areas.
Another representative categories is the technology of sustained release by coating with water-retaining agents. The key technology thereof is to uniformly wrap the core of the fertilizer with a water-retaining agent under particular facilities; or alternatively to firstly wrap the core of the fertilizer with a layer of water-blocking sustained-release coating so as to firstly achieve a function of sustained release of the nutrients, followed by wrapping the outermost layer with a coating of water-retaining agent so as to achieve a function of water retention. Nevertheless, since the water-retaining agent occupies a low proportion within the fertilizer for this kind of coating-type products, the water absorbency is restrained, the sustained release of the nutrient and the sustained release of water are unsynchronized, and the cost for coating is too high. As a result, it is difficult to be applied to the agricultural production.
The technology of combined fertilizer is a technology of organic-inorganic fusion and co-polymerization. The principle of the same is a novel structure substance obtained from organic-inorganic fusion and co-polymerization; the substance is a three-dimensional mesh-like structure hydrophilic group produced from ingenious fusion and co-polymerization of an organic water-retaining factor and an inorganic nutrient factor. It is capable of biodegradable, sustained and controlled release, double retention and double controlled release, integration of water and fertilizer, synchronization of sustained release, resistance to pests and insects, conservation of soils, optimization of microecological environment, improvement of soils, soil fertilizer efficiency, improvement of nutrition and health in human bodies. This fundamentally achieve the strategic objectives of “one saving two reductions” (water saving, fertilizer reduction and pesticide reduction) for the agricultural sustainable development, as advocated in China.
Both of the aforementioned technologies of compounding and coating for water-retaining sustained- and controlled-release fertilizers have their pros and cons, and are not able to achieve a desirable effect in practical production. The organic-inorganic fusion co-polymerization technology has the following advantages: low cost in production, excellent quality with reasonable price; labor-saving and time-saving, energy-saving and beneficial to the environment; nontoxic and harmless, biodegradable, no residuals left; non-volatile, no flow-away; non-combustible, non-explosive; safe for storage and effective in long term; and safe and reliable quality.
In view of these, the present invention is proposed specifically.